The extra cirxuit is already included in the kits - the IR receiver. Just connect the IR receiver (IR photo transistor) to your pic and just add the required software should make it work. There is an example for it to interwork with arduino.

Yup, Allen is correct. Try study the sample code for arduino. The basic concept is the same. You can try discussing what is being done by the arduino code here and try writing your own code for PIC. Basically is just digital input where you have monitor the pulses width. I am sure is fun doing so and you will learn a lot

The reason why the software is so complicated is becos it was for a universal decoder. It can decode NEC, SONY, RC5 (Philips) and RC6 (Not sure) formats. If it were for only one format, the software should be less than half the length. Looks like you have 3 options.

1. Try to learn Arduino C and slowly translate it to Hi-Tech C. 2. Get a simpler remote control kits that only support one format with the PIC and software included 3. Find out which format your remote is sending and just work on that format using the C that you're familiar. Google would be a great help here.